The Internal Revenue Service has been tangling with Los Angeles sports and entertainment mogul Phil Anschutz and former Minnesota Vikings owner Billie Joe “Red” McCombs in a couple of high-profile tax cases involving a strategy that had been marketed to billionaires just like them by Wall Street investment banks.

In the Anschutz case last week, the L.A. Lakers co-owner’s company had been using a complex technique known as a “variable prepaid forward contract” back in 2000 and 2001, agreeing to turn over options on 4 million shares of Union Pacific Resources Group and Anadarko Petroleum Corp. to the investment bank Donaldson, Lufkin & Jenrette, at some point in the future for an upfront payment of $375 million.

Anschutz believed he would be able to defer capital gains taxes of $144 million on the transaction. But the Tax Court agreed with the IRS that since Anschutz’s company not only sold the contracts but also agreed to lend the shares to the bank, which is now owned by Credit Suisse, as well as transferred the share title and voting rights, the variable prepaid forward contract actually should be considered a currently taxable sale. Anschutz plans to appeal the ruling, according to

In the McCombs case, the IRS said the 82-year-old co-founder of Clear Channel Communications owes $45 million after failing to report $213.4 million in long-term capital gains from the sale of 11.3 million shares of Clear Channel in 2002. McCombs borrowed $300 million to finance the purchase of the Vikings, according to Forbes, but pledged 11.3 million shares of Clear Channel as collateral. After the value of the shares began to sink, he agreed to enter into a variable prepaid forward contract with JPMorgan Chase in 2002, with tranches to be settled in the next three years, and to lend 11.3 million shares to the bank that same year.

The IRS, as in the Anschutz case, said the transaction should have been considered a currently taxable sale at the time. McCombs argues that the deals were separate and he didn’t sell any shares back then. He has filed suit against the IRS, and the Tax Court will probably again be called upon to decide the case.

The variable prepaid forward contract may be going the way of the Son of BOSS, SILO, LILO and other transactions that the IRS now considers dubious in nature. If so, a number of billionaires, and the investment banks they favor, will be looking for some new strategies for deferring their taxes.